LED downlights


Postby bif » Tue Feb 10, 2009 9:28 am

Hi, Has anyone experience of using LED lighting? I want to fit recessed downlights into the ceiling of a single storey extension. These wil be fitted directly into plasterboard and 5'' of kingspan insulation. As LED run much cooler than halogen do they require any clearance or ventilation above? I would prefer not to cut right through the insulation if possible. I am looking at fitting 8 'cree' 9w led's; any other advice about wiring, 12v or 240v systems would be appreciated as there does not yet seem to be widespread use of Led's at the moment.
Thanks, Bif
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Postby kbrownie » Tue Feb 10, 2009 12:25 pm

Hi bif, have you already sourced or purchased your LED lights as manufacture instruction are generally to be followed.
I'd expect a 12v transformer to supply them and a control unit.
I'd always recommend avoiding thermal insulation around electrical equipment and cables as it will effect the condition of the cables insulation due to the heating effect.
KB
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Postby bif » Tue Feb 10, 2009 9:00 pm

Hi kbrownie, Thanks for you comments, haven't purchased units yet, just trying to establish suitability but looking at lamps from'cree', American firm I think. Would have some clearance immediately around fitting and heat resistant 'tails' to connect if suitable. Any more thoughts, has anyone used lamps by cree?
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Postby Woody_Dude » Tue Feb 10, 2009 11:03 pm

Kbrownie

It's not only the heating effect and reduced current carrying ability, but also a chemical reaction between some kinds of cables and polysterene insulation. If in direct contact it can degrade cable over time, so causing premature failure.
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Postby kbrownie » Thu Feb 12, 2009 3:46 pm

Hi bif
I agree with Woody_Dude. Yes not advisable to use polystyrene around electrical cables as it does have a chemical reaction known as marring, this can degrade the insulation around the cable. So forget about polystyrene insulation around cable insallations and elecrical equipment.
The general points are try to avoid cable runs through thermal insulation, try to clip away and level space or lay it on top of the insulation giving it space/ventalation for heat to disapate.
If cable does need to run through insulation a cable calculation needs to be made in compliance of BS7671. This will increase your cable csa size.
Leave at least 150mm area around light fittings, clear of insulation.
Follow manufacturers instruction regarding the lights, fitted them in the past and currently doing a job with them now but I am no expert on them. I know they are getting more popular, may need to read up on them myself.
Remember to stay safe.
KB
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Postby bif » Fri Feb 13, 2009 4:22 pm

Thanks for your comments, didn't know about insulation reacting with the cable, will route it away or run through conduit.
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